静电“S^+X^-I^+”组装途径合成Ti-MCM-41分子筛及其催化氧化性能

SYNTHESIS OF Ti-MCM-41 MOLECULAR SIEVES BY ELECTROSTATIC S^+X^-I^+ ASSEMBLY PATHWAY AND ITS CATALYTIC OXIDATION PERFORMANCE

采用静电“S+ X-I+ ”组装途径合成了骨架含钛的中孔分子筛Ti MCM 4 1,系统研究了不同因素对分子筛结构的影响以及Ti MCM 4 1分子筛对不同烯烃的催化氧化性能 .在强酸介质中由于钛源的高度溶解导致只有部分Ti进入分子筛骨架 ,骨架钛含量随HCl/TEOS增大而减小 ,分子筛收率及晶胞参数 (a0 )、孔道壁厚(δwt)随HCl/TEOS的增大而增大 .在较宽的C16TMABr /TEOS (0 3～ 1 0 )和H2 O/TEOS (6 0～ 12 0 )范围内均能得到高度有序的Ti MCM 4 1分子筛 .采用丙酮 水混合溶剂萃取法可以有效回收分子筛原粉中的模板剂而不影响分子筛的结构有序度 .以双氧水或分子氧为氧化剂 ,Ti MCM 4 1分子筛对多种烯烃均具有催化氧化活性 .静电“S+ X-I+ ”组装途径合成的Ti MCM 4 1分子筛催化氧化活性略低于水热晶化法合成的Ti MCM 4 1分子筛 .

Ti-containing mesoporous molecular sieves Ti-MCM-41 were synthesized by electrostatic S+X-I+ assembly pathway. Influences of different factors on the structure of Ti-MCM-41, as well as catalytic oxidation performance of Ti-MCM-41 on many kinds of alkenes were investigated systematically. Only a part of Ti source could be introduced into the framework of Ti-MCM-41 molecular sieve due to the high solubility of Ti under strongly acidic conditions. Ti content in framework decreased with the increase of HC1/TEOS, while the yield, the unit cell parameter a0 and the framework wall thickness δw; of Ti-MCM-41 molecular sieve increased with the increase of HC1/TEOS. The highly ordered of Ti-MCM-41 molecular sieve could be obtained in the wide range of C16TMABr/TEOS (0.3-1.0) and H2O/TEOS (60-120). The template could be effectively recovered from the Ti-MCM-41 precursor by extraction with a mixed solvent of acetone-water, which would not change the ordered structure of Ti-MCM-41 products. Ti-MCM-41 showed catalytic activity to oxidation of many alkenes with hydrogen peroxide or molecular oxygen as oxidizer. The catalytic activity of Ti-MCM-41 from electrostatic S+X-I+ assembly pathway was a little lower than that of Ti-MCM-41 from hydrothermal crystallization.